Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

Pseudoreplication is defined. as the use of inferential statistics to test for treatment effects with data from experiments where either treatments are not replicated (though samples may be) or replicates are not statistically independent. In ANOVA terminology, it is the testing for treatment effects with an error term inappropriate to the hypothesis being considered. Scrutiny of 176 experi- mental studies published between 1960 and the present revealed that pseudoreplication occurred in 27% of them, or 48% of all such studies that applied inferential statistics. The incidence of pseudo- replication is especially high in studies of marine benthos and small mammals. The critical features of controlled experimentation are reviewed. Nondemonic intrusion is defined as the impingement of chance events on an experiment in progress. As a safeguard against both it and preexisting gradients, interspersion of treatments is argued to be an obligatory feature of good design. Especially in small experiments, adequate interspersion can sometimes be assured only by dispensing with strict random- ization procedures. Comprehension of this conflict between interspersion and randomization is aided by distinguishing pre-layout (or conventional) and layout-specifit alpha (probability of type I error). Suggestions are offered to statisticians and editors of ecological j oumals as to how ecologists' under- standing of experimental design and statistics might be improved.

/pdf/pseudoreplication-and-the-design-of-ecological-field-44o8kzdaoi.pdf

Pseudoreplication and the Design of Ecological Field Experiments

Evolution and measurement of species diversity

General guidelines for use of wild mammal species are updated from the 1998 version approved by the American Society of Mammalogists (ASM) and expanded to include additional resources. Included are details on marking, housing, trapping, and collecting mammals. These guidelines cover current professional techniques and regulations involving mammals used in research. Institutional animal care and use committees, regulatory agencies, and investigators should review and approve procedures concerning use of vertebrates at any particular institution. These guidelines were prepared and approved by the ASM, whose collective expertise provides a broad and comprehensive understanding of the biology of nondomesticated mammals in their natural environments.

/pdf/guidelines-of-the-american-society-of-mammalogists-for-the-2g7v778e1f.pdf

Guidelines of the american society of mammalogists for the use of wild mammals in research

The degree of herbivory and the effectiveness of defense varies widely among plant species. Resource availability in the environment is proposed as the major determinant of both the amount and type of plant defense. When resource are limited, plants with inherently slow growth are favored over those with fast growth rates; slow rates in turn favor large investments in antiherbivore defenses. Leaf lifetime, also determined by resource availability, affects the relative advantages of defenses with different turnover rates. Relative limitation of different resources also constrains the types of defenses. The proposals are compared with other theories on the evolution of plant defenses.

https://science.sciencemag.org/content/sci/230/4728/895.full.pdf

Resource Availability and Plant Antiherbivore Defense

Populations of the California vole, Microtus californicus , were followed at two sites near San Francisco Bay in order to investigate changes in diet and condition of these cycling microtine rodents. Mark and recapture analyses provided information on condition during seasonal (season to season) and annual (year to year) fluctuations, and snap trapping provided stomach samples for dietary analyses and carcasses for determinations of reproductive condition and fat reserves.

Seasonal changes in condition were found to be correlated with dietary changes. The end of the breeding season in late spring was associated with low growth rates, low survival rates, and low fat reserves. At the same time the vegetation was drying, and the diet changed from one dominated by grass stems and leaves to one dominated by grass seeds. Breeding and adult growth sometimes began before the autumn rains while grass seeds were still the major dietary item, but occasional meals of green forbs and perennial grass were also taken at this time.

Three annual grasses, Lolium multiflorum, Avena fatua , and Bromus rigidus , were preferred foods and formed the bulk of the winter diet at both low and high populations. The standing crop and seed production of these grasses were severely reduced by high vole populations. Reduction in food availability and quality might have caused the delay in the start of the breeding season, the low fat reserves and the continued population decline that were observed after the peak population.

These results indicated that nutritive factors could be involved in microtine population cycles at low latitudes and point to the need for further research on diet quality and nutritional physiology of Microtus .

Condition and diet of cycling populations of the California vole, Microtus californicus.

Nutrition, spacing behavior, and predation have been proposed as major factors limiting the population density of microtine rodents (lemmings and voles). How- ever, there is no general agreement as to the relative importance of these factors, nor have their interactions been carefully examined. This paper reports on a factorial experiment designed to test the general hypothesis that predation and the availability of high-quality food act simultaneously and additively to limit densities of microtine rodent populations. Our results showed that supplemental high-quality food significantly increased body growth rates, proportion of adults in the population, adult male body size, reproductive activity, recruitment, and density of prairie vole populations. Food availability had no effect on survival nor on sex ratio in any of the 3 yr of this study. Protection from predation significantly increased adult survival (somewhat sporadically), recruitment, and density, but it did not directly affect growth, population structure, or reproduction. Improved survival of young animals could not be detected, but increased recruitment suggested that it may have occurred, perhaps before the young reached trappable size. Food supplemen- tation and protection from predation generally had additive and equal effects on density. The only significant food-predator interactions were for body growth rates and adult body size. The presence of predators appeared to inhibit the growth response to supplemental food, possibly because of more restricted movement and, therefore, less access to food.

Effects of food availability and predation on prairie vole demography: a field experiment'

Densities and demography of prairie voles ( Microtus ochrogaster ) vary widely in different habitats, and dramatic, cyclical changes in population densities occur. We provided high quality supplemental food (rabbit pellets) to a population in relatively unfavorable habitat (an old bluegrass pasture) to test the hypothesis that differences in food quality can account for those trends. Throughout the winter the experimental population showed higher breeding intensity, better adult survival, and higher body growth rates than the control population. As a result, the supplemental population reached densities (135/ha) 50% higher than those of the control population (90/ha). Moreover, body growth, litter size, and density remained higher in the supplemental population during the following spring and summer. However, supplemental feeding did not prevent or delay declining densities that occurred in late summer and autumn in both populations. We conclude that quality of available food influences the amplitude of population fluctuations of the prairie vole, but some other factor(s) must initiate the periodic declines.

Influence of Supplemental Feeding on a Vole Population

Availability of food may play a number of different dynamical roles in rodent–vegetation systems. Consideration of a suite of rodent–vegetation models, ranging from very simple ones to a model of medium complexity tailored to a specific system (brown lemmings at Point Barrow, Alaska, USA), suggested several general principles. If vegetation grows logistically following an herbivory event (a standard assumption of previously advanced models for herbivore–plant interactions), then almost any biologically reasonable combinations of parameters characterizing rodent–vegetation systems would result in population cycles. We argue, however, that the assumption of logistic growth of the food supply may be appropriate for only a few species, such as moss-eating lemmings. The dynamics of food supply for many arvicoline (microtine) rodents may be better described by a “linear initial regrowth” model, which exhibits globally stable dynamics. If this is so, quantitative interactions with food supply are unlikely to exp...

http://www.sysecol2.ethz.ch/Refs/EntClim/T/Tu060.pdf

Availability of food and the population dynamics of arvicoline rodents

We compared the effects of habitat quality on dispersal, demography, dynamics, and fitness of prairie vole (Microtus ochrogaster) and meadow vole (M. pennsylvanicus) populations by manipulating habitat patches in experimental landscapes. Four habitat patches in each of four replicate landscapes differed in availability of high-quality food and amount of vegetative cover in a 2 × 2 factorial design. High cover had a strong positive effect on basic habitat quality, as reflected by the performance of founders early in the season, but supplemental food had only a small effect. Population growth ceased for prairie voles after week 18 (mid-October) when densities had reached much higher levels in habitats with high cover (260 ± 27 voles/ha in high cover with either high or low food; mean ± 1 se) than in habitats with low cover (115 ± 38 voles/ha in high food, low cover and 60 ± 15 voles/ha in low food, low cover). Population growth had ceased in three habitat types for meadow voles by week 20 at much higher den...

George O. Batzli

Papers

Condition and diet of cycling populations of the California vole, Microtus californicus.

Effects of food availability and predation on prairie vole demography: a field experiment'

Influence of Supplemental Feeding on a Vole Population

Availability of food and the population dynamics of arvicoline rodents

The influence of habitat quality on dispersal, demography, and population dynamics of voles